It is the long-range goal of this project to study the co-oxygenation of chemicals, i.e., benzo(a)pyrene (BP)-7,8-diol during the metabolism of arachidonic acid (AA) by guinea pig lung, ram seminal vesicle, mouse skin, human lung, and cells grown in tissue culture. BP-7,8-diol was oxidized to 7,10/8,9 tetral by prostaglandin synthetase by all the tissues examined. Electrophilic metabolites of BP-7,8-diol were covalently bound to protein. With human lung the rate of conversion of BP-7,8-diol by the AA dependent system was greater than the NADPH-dependent oxidation. AA-dependent oxidation produced only 7,10/8,9 tetral but NADPH-dependent oxidation formed 4 tetrols. We found that during the oxidation of AA to PG's, a number of aromatic amines (including several insecticides) are demethylated. The significance of the oxidation of chemicals during PG formation, as related to chemical-induced toxicity or carcinogenesis is being examined.